JPH04107494A - Safety device of image formation device - Google Patents

Abstract

PURPOSE:To enable accurate temperature control over a heat fixation part by setting a comparison reference time according to at least one of the input voltage and the temperature of the heat fixation part after power-on operation which affect the rising time of the temperature. CONSTITUTION:A continuous electric feeding limit time is set by storing the ROM of a CPU 8 with a table of continuous electric feeding limit time data predetermined by the relation between the temperature of a fixing roller and the input voltage to a fixing heater 2 which affects the rising time of the temperature of the fixing roller and reading corresponding continuous electric feeding limit time out of the ROM according to the temperature of the fixing roller and the input voltage to the fixing heater 2 which are detected when a power switch is turned on. Thus, the comparison reference time as the reference of the temperature control is set according to at least one of the input voltage and temperature of the heat fixation part after power-on operation which affect the rising time of the temperature. Consequently, the temperature control over the heat fixation part is accurately performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a safety device for an image forming apparatus, and particularly to a temperature control device for a heat fixing section thereof.

(Prior Art) Conventionally, in image forming apparatuses such as copying machines and laser printers, heat fixing devices for fixing transferred images onto recording paper have been disclosed in Japanese Patent Publication No. 1, Japanese Patent Publication No. 62-4715, and Japanese Patent Application Laid-open No. 61-11.
As shown in Japanese Patent No. 0182, if the temperature of the fixing roller constituting the heat fixing device does not reach the predetermined temperature even after a predetermined period of time has passed since the power switch is turned on, it is determined that an abnormal state has occurred and the heater of the heat fixing device is turned off. A safety device is provided to cut off the electricity.

(Problem to be Solved by the Invention) In the above-mentioned conventional device, the temperature rise time is greatly affected by the operating environment temperature, input voltage, etc. Even if there is, there is a range of 85V to 1]5V. Comparing the rise time in this case, 85V to 115V is 2
What is the difference in times?

Therefore, the length of the predetermined time that is the basis for determining an abnormal state as described above is set in consideration of the worst-case scenario (high environmental temperature, low input voltage) for parameters that have a large influence on the temperature rise time. .

Therefore, for example, if the temperature detection element is malfunctioning and the temperature cannot be detected, and the environmental temperature is high or the input voltage is high, the temperature of the fixing roller will rise rapidly before the predetermined time elapses, causing thermal fixation. There were defects that caused damage to the equipment.

An object of the present invention is to accurately control the temperature of a heat fixing section,
An object of the present invention is to provide a highly safe safety device for an image forming apparatus.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a temperature detection means for detecting the temperature of a heat fixing section, an energization control means for controlling energization to the heat fixing section, and a power-on A timer that measures the continuous energization time to the heat fixing unit, and an abnormality in the heat fixing unit when the temperature of the heat fixing unit does not reach the set temperature even if the continuous energization time reaches a predetermined comparison reference time. Input voltage detection for detecting the magnitude of input voltage to the thermal fixing section in the safety device for an image forming apparatus, the safety device comprising: a control means for determining that the current supply control means cuts off the current supply to the thermal fixing section; The apparatus is characterized in that the comparison reference time is set based on detection data of at least one of the temperature detection means and the input voltage detection means after power is turned on.

(Function) Because the above method is adopted, the comparison reference time, which is the standard for determining whether the heat fixing unit is abnormal, is determined by the input voltage and temperature to the heat fixing unit after the power is turned on, which affects the temperature rise time. Since the comparison reference time is set based on at least one of the above, the comparison reference time can be set accurately and reliably, and the temperature of the heat fixing section can be accurately controlled by the control means.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, in which 3 is a known heat fixing section for fixing a transferred image on recording paper, and includes a fixing heater 2 and a fixing roller (not shown). Reference numeral denotes a power source for the fixing heater 2, 4 a fuse which is an element for preventing excessive temperature rise, 5 an energization control means including a switching circuit for controlling energization to the heat fixing section 1, and 6 a fixing roller of the heat fixing section 1, etc. Temperature detection means is installed near the fuser heater 2 to detect the temperature; 7 is an input voltage detection means for detecting the magnitude (value) of power input to the fixing heater 2 after a power switch (not shown) is turned on; 8 is described later. Continuous energization limit time (
A table of comparison reference time) is stored in a ROM (not shown) which is a storage means, and a CPU (which is a control means) which controls the energization control means 5 based on the continuous energization limit time.
9 is a timer that measures the continuous power supply time to the fixing heater 2.

The basic operation of temperature control for the fixing unit in the above embodiment is as follows:
The timer 9 measures the continuous energization time to the fixing heater 2 from the time the power switch is turned on, and the CPU 8 receives the time data of the continuous energization time from the timer 9 and the temperature data of the fixing roller from the temperature detection means 6. When the fixing roller does not reach a predetermined temperature even after the continuous energization time reaches a predetermined continuous energization limit time, the thermal fixing unit 1
This CPU8 is judged to be in an abnormal state.
When it is determined that there is an abnormality in
An abnormality signal is output to the fuser heater 2, and the power supply control means 5 prevents the heat fixing section 1 from overheating by cutting off the power supply to the fixing heater 2.

In this embodiment, the continuous energization limit time is set by C.
As shown in Table 1, the PU8's ROM contains a table of continuous energization limit times predetermined based on the relationship between the temperature of the fixing roller and the input voltage to the fixing heater 2, which affects the rise time of the temperature of the fixing roller. This is done by storing the following and reading out the corresponding continuous energization limit time from the ROM based on the temperature of the fixing roller detected when the power switch is turned on and the voltage input to the fixing heater 2.

Table 1 In Table 1, for example, if the temperature of the fixing roller is 15° C. and the input voltage is 98 V when the power switch is turned on, the continuous energization limit time is set to 45 seconds.

The temperature control of this embodiment will be explained in more detail with reference to the flowchart shown in FIG. That is, when the power switch is turned on (81), the temperature of the fixing roller and the input voltage to the fixing heater 2 at that time are detected by the temperature detection means 6 and the input voltage detection means 7 (S2), and the temperature of the fixing roller is detected. Having received the data and the input voltage data to the fixing heater 2, the CPU 8 reads the continuous energization limit time corresponding to each data from the continuous energization limit time table in Table 1 (S3). Thereafter, the CPU 8 controls the energization control means 5.
S4 to output power to the fixing heater 2.
), and at the same time timer 9 is used to measure the energization time.

Also, the temperature of the fixing roller has not reached the set temperature (
S5 N○), and if the continuous energization time measured by timer 9 exceeds the set continuous energization limit time (
If YES in S6), the CPU 8 determines that the thermal fixing section 1 is abnormal, and causes the power supply control means 5 to cut off the power supply to the fixing heater 2 (S7).

In this way, the continuous energization limit time, which is the comparison standard time that is the standard for temperature control of the heat fixing section 1, is determined by the temperature of the heat fixing section 1 (temperature of the fixing cola), which affects the temperature rise time, and the temperature of the heat fixing section 1, which affects the temperature rise time. By setting the temperature in consideration of the input voltage to I (the input voltage to the fixing heater 2), temperature control can be performed accurately, and fires due to overheating can be reliably prevented, increasing safety. Furthermore, overheating is suppressed before fuse 4 blows out due to overheating, and fuse 4
This can also contribute to reducing costs associated with replacement.

In the above embodiment, the continuous energization limit time refers to both the temperature of the thermal fixing unit 1 (temperature of the fixing roller) and the input voltage to the thermal fixing unit 1 (input voltage to the fixing heater 2). However, it is conceivable that the continuous energization limit time can be set using either one of the two types of data.

(Effects of the Invention) As described above, according to the present invention, the setting of the comparison reference time, which is the standard for temperature control, affects the input voltage and temperature to the heat fixing section after power is turned on, which affects the temperature rise time. Therefore, the temperature of the heat fixing section can be accurately controlled, and a highly safe safety device for the image forming apparatus can be provided.

[Brief Description of the Drawings] Fig. 1 is a configuration diagram of an embodiment of the safety device of the image forming apparatus of the present invention, and Fig. 2 is a flowchart relating to temperature control of this embodiment. a power source; 5. degree detection means; 8. control means; 2. Fixing heater, 3. Current supply control means, 6.. Temperature 7.. Input voltage detection means, 9.. Timer.

Claims (1)

[Claims] a temperature detection means for detecting the temperature of the heat fixing section; a current supply control means for controlling the supply of electricity to the heat fixing section; a timer for measuring the continuous supply of electricity to the heat fixing section from the time the power is turned on; control means for determining that there is an abnormality in the heat fixing section when the temperature of the heat fixing section does not reach the set temperature even after reaching a predetermined comparison reference time, and causing the power supply control means to cut off the power supply to the heat fixing section; The safety device for an image forming apparatus includes an input voltage detection means for detecting the magnitude of the input voltage to the heat fixing section, and the comparison reference time is set to the temperature detection means and the input voltage detection after the power is turned on. 1. A safety device for an image forming apparatus, characterized in that the safety device is configured to be set based on detection data of at least one of the device and the device.